The present invention relates to a new and distinct cultivar of Heuchera given the cultivar name of ‘TNHEUGA’. Heuchera is in the family Saxifragaceae. Heuchera ‘TNHEUGA’ originated as a controlled cross using Heuchera B107-4, a proprietary, unnamed plant as the seed parent, and Heuchera B121-3, a proprietary, unnamed plant as the pollen parent. The trademark designation is ‘Grande™ Amethyst’.
Compared to the seed parent B107-4, the new cultivar has leaves that have a stronger purple-black color, flowers on shorter inflorescences, and a larger habit.
Compared to the pollen parent B121-3, the new cultivar has leaves that have a stronger purple color.
Compared to Heuchera ‘FOREVER™ Purple’, U.S. Plant Pat. No. 26,358, the new cultivar has a purple-black foliage rather than rose to light plum.
Compared to Heuchera ‘Velvet Night’, an unpatented plant, the new cultivar has larger leaves and habit, with leaves a darker purple and black.
This new Heuchera is uniquely distinguished by:                1. large habit with leaves that are purple and ruffled,        2. a great landscape or container plant,        3. great winter foliage color and hardiness,        4. a high crown count, and        5. excellent vigor.        
This new cultivar has been reproduced only by asexual propagation (tip cuttings and tissue culture). Each of the progeny exhibits identical characteristics to the original plant. Asexual propagation by cuttings and tissue culture using standard micropropagation techniques with terminal and lateral shoots, as done in Canby, Oreg., shows that the foregoing characteristics and distinctions come true to form and are established and transmitted through succeeding propagations. The present invention has not been evaluated under all possible environmental conditions. The phenotype may change with variations in environment without a change in the genotype of the plant.